Method and apparatus for delivering blood oxygen association curve information

ABSTRACT

Method of measuring the oxygen association state of blood samples, which includes the steps of disposing a blood sample within a blood-receiving receptacle, providing a controlled atmosphere chamber, incubating the sample by placing it in the chamber and controlling said atmosphere therein so as to maintain the humidity, temperature, and carbon dioxide content of the atmosphere at substantially constant levels, and thereafter analyzing the sample by changing the concentration of oxygen in said chamber from time to time while observing the changes of oxygen association of the sample with respect to the concentration of oxygen within the chamber. 
     An apparatus which includes two sample holders receiving slides adapted to position the samples in the chamber in incubating and analyzing position, respectively.

BACKGROUND OF THE INVENTION

The present invention relates generally to improved methods andapparatus for blood analysis, and more particularly to improved methodsand apparatus for handling blood samples during a determination of theoxygen association of the blood, and charting the relation between thedegree of such association and the concentration of oxygen which is ineffective contact with the sample.

Normally, a chart is prepared on an instrument designed to record aseries of readings representing the degree of oxygen associationexisting at any given oxygen concentration. The chart is used fordiagnosis of clinical conditions existing in the patient by medicaland/or other technicians.

According to the invention, it has been discovered that increasedaccuracy and reproducibility of these characteristic curves can beobtained if the blood samples are incubated or pre-treated in anatmosphere which is controlled with respect to certain variables beforethe samples are observed to determine the association curves.

It has also been determined that this pre-treatment or incubation can beachieved without loss of time by using the apparatus and method of theinvention; specifically, while one sample is being analyzed in oneportion of the analysis device, the other sample may be incubated inanother portion of the analysis device. Subsequently, the just-analyzedsample is removed and a new sample is inserted in the analysis devicefor incubation while the just-incubated sample is being analyzed.

The novel analysis device provides a highly effective seal againstatmospheric contamination, and serves to hold two samples, one each inan upper and lower slide unit, respectively. Both slides includerecesses adapted to receive the analysis devices, and the upper slidealso includes an aperture therein to permit exposure of the sample inthe lower slide to the conditioning atmosphere within the chamber whilethe upper slide is in its axially innermost position. The two slidesreciprocate among fully inserted, partially inserted, and withdrawnpositions, thereby permitting samples to be analyzed, incubated andwithdrawn, respectively.

While the general method of analysis is known, the present inventionalso comprehends certain improvements in the method other than thosereferred to above.

While the reasons for the success of the invention are not known withcertainty, it is thought possible that the exposure of the blood samplesto known degrees of humidity and temperature, and known concentrationsof carbon dioxide tends to stabilize the blood mechanically, renderingthe samples capable of more accurate analysis.

An object of the present invention is to provide an improved apparatusand method for analyzing blood samples.

Another object of the invention is to provide a blood sample analysismethod which includes incubating a blood sample under controlledconditions before analyzing it for oxygen association in relation tooxygen concentration.

Still another object of the invention is to provide an analysis methodwherein a series of samples are incubated, analyzed and removed,respectively, with each incubated sample being analyzed as a subsequentsample is being incubated.

Another object is to provide an apparatus which includes plural bloodsample holder slides arranged for movement between positions permittingthe samples to be inserted or removed, incubated or analyzed, with theslides being operable separately of each other in the sequence referredto herein.

Another object is to provide a method of analysis which includes the useof an optical analysis beam comprised of frequencies not heretofore usedfor this purpose.

These objects and advantages are achieved by providing a method of bloodanalysis which includes incubating a blood sample under controlledatmospheric conditions before analyzing it, and by providing a novelsample holder apparatus permitting samples to be so incubated beforeanalysis.

The foregoing and other objects and advantages of the invention,including those inherent therein are achieved in practice by providing amethod which includes the steps of placing a blood sample to be analyzedin a chamber wherein the atmosphere may be controlled, and permittingsaid sample to incubate before analysis of the degree of oxygenassociation thereof is made. The invention also achieves its objects byproviding a novel sample holder analysis device permitting blood samplesto be maintained within the controlled atmosphere chamber for incubationand analysis, respectively, with one sample being positioned foranalysis while the other is positioned away from the light beam used tomake the analysis, in a position for incubation. The invention alsoachieves improved operating advantages by using wave lengths in thelight source which have not been heretofore used for this purpose.

The exact manner in which the foregoing objects and advantages areachieved in practice will become more apparent as reference is made tothe following detailed description of the preferred embodiments of theinvention set forth by way of example and shown in the accompanyingdrawings, in which light reference numbers indicate corresponding partsthroughout the several figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view, partly diagrammatic in character and partly invertical section, showing one form of apparatus used in the practice ofthe invention.

FIG. 2 is a side elevational view of the analysis device, shown apartfrom the chamber and showing both slide units in the fully insertedposition;

FIG. 3 is an end elevational view of the analysis device, showing themanner in which the sample holders are received within the analysischamber;

FIG. 3a is a fragmentary view, on an enlarged scale, showing the meansfor retaining the mounting portion of the analysis device assemblywithin a wall of the chamber;

FIG. 4 is a end elevational view, on a enlarged scale, showing theanalysis device when viewed from the inside of the chamber;

FIG. 5 is an exploded view, taken approximately along the line 5--5 ofFIG. 4, of certain portions of the device, showing the manner ofaffixing it to the mounting portion of the assembly;

FIG. 6 is a top plan view of the upper slide unit which receives one ofthe sample holders containing blood samples;

FIG. 7 is a top plan view of the lower slide unit; and

FIG. 8 is a partial perspective view of the apparatus showing theanalysis device disposed in a position of use and forming a part of thefront wall of a controlled atmosphere chamber.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

While the method and apparatus of the present invention may be practicedin different forms, a description thereof will be made with respect to aprocess wherein blood samples are prepared, placed within a controlledatmosphere chamber, and analyzed by passage of light therethrough. Astrip chart recorder is used to record successive readings which relatethe degree of oxygen association of the blood in the sample to theconcentration of oxygen present within the chamber. According to theinvention, the atmosphere within the chamber is controlled with respectto temperature, humidity and carbon dioxide content, and means areprovided for purging the chamber of the carrier gas, or purging thechamber of oxygen, as desired, following which metered amount of oxygenare introduced into the chamber for purposes of reacting with the bloodsample. Analysis of blood samples by the method referred to herein isgenerally known to those skilled in the art. The invention hereincomprises an improvement in the inventions described in and claimed inmy previously issued U.S. Pat. No. 3,854,878, dated Dec. 7, 1974 and inthe method and apparatus described in application Ser. No. 504,112,filed Sept. 9, 1974 in the name of Eugene K. Achter now abandoned, saidapplication in turn being a continuation-in-part of application Ser. No.466,089, filed May 1, 1974 by Eugene K. Achter now abandoned.

As described in the above identified patents and applications, bloodsamples are taken to end points consisting of complete oxygenassociation or substantially no oxygen association, and thereafter theyare reoxygenated or deoxygenated in a series of steps, with the degreeof association and the relative concentration of oxygen being noted at aplurality of reading points. Subsequently, or simultaneously, a curve isconstructed which illustrates the relation of the association of oxygenin the blood to the degree of concentration of oxygen present within thechamber wherein the analysis was made. Charts of this sort having acharacteristic tape are useful for clinical purposes.

Referring now to the drawings, FIG. 1 shows the invention to betypically embodied in an instrument which includes an analysis chamber12 contained within a housing generally designated 14. The housing 14 isshown to include an end wall 16, a top wall 18 and a bottom wall 20,said walls, together with side walls, (not shown) cooperating to definethe enclosed chamber 12. Portions of the top and bottom walls 18, 20respectively, define top and bottom apertures 22, 24, are placed lenses26, 28, or other photo transmissive means.

According to the preferred embodiment of the invention, a light beam 30passes through the lenses 28, 26 from a light source 32 to a beamsplitter 34 located outside the chamber. In so doing, the beam 30 passesthrough the sample 36 which is received in a holder 38 within the pocket40 of the upper slide unit 42.

As the beam contacts the splitter 34, a portion of it passestherethrough, subsequently through the filter 44, and onto lightresponsive means in the form of a first photo diode 46. Another portionof the beam is directed from the beam splitter through a second filter48 and impinges on a second photo diode 50. The outputs of the photodiodes are united in a log-ratio amplifier 52, the output signal ofwhich is directed to an XY-recorder, the operation of which, being knownto those skilled in the art, need not be further described. According tothe invention, the other input to the XY-recorder 54 is from the oxygenelectrode 56. In a preferred form of the invention, a chart is preparedwherein the concentration of oxygen within the chamber forms one axis ofchart and the degree of oxygen association forms the other axis,normally the Y-axis. Thus, the curve which results is one wherein the Xor horizontal axis shows the concentration of oxygen present and the Yor vertical axis shows a degree of oxygen association within the bloodsample. The preferred form of instrument moves the chart within therecorder in response to a signal from the oxygen detector 56.

Referring now again to the make-up of the controlled atmosphere chamber,it will be noted that a fan 58 is provided to insure distribution of theoxygen or other gases in the chamber so that sampling thereof asdetected by the oxygen electrode 60 will be accurate. An inlet 62 isprovided for a "neutral" or carrier gas 62 as in an inlet for theoxygen-containing gas 64.

As is known to those skilled in the art, the carrier gas is preferablyone comprised of nitrogen, having 5.6% CO₂ mixed therewith. The oxygengas consists of 25% oxygen, the same 5.6% CO₂ and the remaindernitrogen.

As shown in the drawings, a thermostat schematically shown as 66 isprovided, as is a humidity detector 68. In this manner, the atmosphericvariables within the chamber 12 may be accurately controlled.

Referring again to FIG. 1, the analysis device generally designated 70is shown to be contained within a mounting portion 72 which is receivedwithin the end wall 16 of the chamber 12. The device 70 includes anupper slide unit 42 and lower unit 74, an inner slide frame 76, an outerslide frame 78, and inner and outer seals 80, 82.

FIG. 2 shows that the finger receiving portions 84, 86 of the upper andlower slides respectively are flush with each other when both slides arein the forward most position. As shown in FIGS. 3 and 3a, the mountingportion 72 of the analysis device assembly 70 is received within thefront wall 16, and is preferably held in place therein by a detentmechanism generally shown at 88. FIG. 3a shows the mechanism 88 toinclude a ball 90, a spring 92 urging the ball axially of the recess 94and into a shallow pocket 96 in the end wall 16 of chamber 12. Inpractice, the opening in the end wall 16 which receives the mounting 72closely approximates the size of the mounting portion 72 so that asubstantially gas type fit between these parts is achieved.

Referring now to FIG. 4, the inner slide frame 76 is shown to be of agenerally C-shaped configuration, and to include a mounting bracket 98extending downwardly therefrom. The upper and lower slides 42, 74 arereceived within the slide frame, which permits of axial movement of theslides with respect to each other. The top inner seal 80 and the flange98 are shown to include elongated slots 100, 102 for fasteners 104, 106,thus permitting relative movement of the frames and seals with respectto the mounting portion 72.

FIG. 5 shows that openings 118, 110 in the mounting portion 72 permitthe fasteners 104, 106 to extend through the wall 72 and respectivelythreadly engaged into the outer seal 82 and the outer slide frame 78.With the slides in place within the slide frames, the seals 80, 82 aremoved vertically until a snug fit is achieved between them and the uppersurfaces of the upper slide 42. Thereupon the fasteners are tightenedand effective seal is achieved.

FIG. 6 shows that the upper slide 42 includes a pocket 40 to which thesample holder 38 is received. An inwardly extending annular land 112prevents the sample holder 38 from falling out of the pocket 40. Aventing aperture 114 is also provided in upper slide 42 being axiallyspaced from the aperture 40 toward the outer or non-entry end of theslide. A thumb receiving, serrated actuator 84 forms the outer ornon-entry end of the slide 42. Detent notches 116, 116' are providedalong one edge of the slide 42, to insure that the slide will index to adesired axial position which can be detected by the operator. An axiallyextending groove 118 is provided in the other edge of the slide 42 forreceiving a guide boss 120 (FIG. 4).

Referring now to FIG. 7 the lower slide 74 is shown to resemble theupper slide 42 in most respects, but differs therefrom in that there isnot venting aperture in slide 74 details. The pocket 122 is defined by acylindrical wall 124 of the slide and by an inner annularly landextending 126. A glass sample holder 38, to be described later, isreceived within the pocket 122 in the lower slide 74. Also providedalong one edge of the slide 74 is a groove 128 for receiving the boss130 (FIG. 4) and as well the opposite edge of the slide 74 is providedwith detent notches 132 spaced axially therealong. The fingermanipulative tab 86 is similar, but located in an opposite hand relationto the position tab 84 of the upper slide 42.

Referring now to FIG. 8, a perspective view of the face of the bloodanalysis chamber 12 is shown with one slide 74 being disposed partiallywithin the chamber 12 and the other slide 42 being completely insertedtherein. The arrows indicate the direction of movement of the respectiveslides into and out of the chamber, which is only partially shown. Aspointed out above, each slide 42, 74 may be indexed in various axialpositions within or without the chamber 12, insuring that the samplewill be correctly indexed for incubation or viewing, as desired.

Referring again to FIG. 5, it will be noted that the exterior or outerslide frame 78 includes upper and lower detents 134, 136, which engagethe notches 116, 132 in slides 42 and 74 respectively. These detents134, 136 are substantially identical to the structure shown in FIG. 3abeing spheres urged by small springs similar to the spring 92 and sphere96 shown in FIG. 3a.

The sample holders 38 are discoidal in form being adapted to fit withinthe respective pockets 40 and 122 of the respective slides 42 and 74.Obviously the sample holders may be of a variety of constructions justso long as they are transparent for the passage of light waves and are,at least in part, oxygen permeable so as to permit oxygen to contact theblood sample contained therein. Finally, the diameter or size of thediscoidal holder should be such that it will fit within the pockets 40and 122 and bear against lands 112 and 126 respectively. Preferably thesample holders are of such diameter or size that there is somefrictional contact between their outer edges and the cylindrical wallsof the aforesaid pockets whereby they will be retained in place yet canbe readily expelled from pockets 40 and 122 by modest finger pressure. Amost preferred sample holder is the type having a lower glass disc andan upper oxygen permeable membrane of the type described in co-pendingapplication Ser. No. 504,112, filed, Sept. 9, 1974 and including a lowerglass and an upper oxygen permeable membrane.

Referring now to the operation of the instrument 10, it will be assumedthat a plurality of samples have been prepared by placing blood betweena lower glass and an upper oxygen permeable membrane and that thesamples have been placed in sample holders 36. The instrument 10 isoperated by turning on the temperature and humidity controls of theknown type, typically adjusting conditions inside the chamber 12 to 37°C and 100% relative humidity. A sample holder 38 is placed in the pocket40 of the upper slide 42, and placed in the chamber. The instrument iscalibrated by purging the chamber, first with oxygen so as to completelyoxygenate the blood, then with the nitrogen-CO₂ mixture so as tocompletely deoxygenate the blood. Accordingly, the machine will becalibrated for 0% and 100% oxygen. It will be assumed that the firstspecimen has been incubated within the chamber for a suitable period oftime, such as for example, 20 minutes. At this point, a second sampleholder is inserted in the apparatus, this time into the pocket 122 inthe lower slide 74. The slides are then manipulated to the positionshown in FIG. 8 and FIG. 1, with the upper slide 42 fully within thechamber and the lower slide 74 in a intermediate position. This alignsthe pocket 40 with the light beam 30. In the position of the slides justdescribed, the venting aperture 114 overlies the pocket 122 in the lowerslide 74 permitting contact between the controlled atmosphere and secondspecimen. Assuming the chamber 12 to have been purged with nitrogen andthe sample to be deoxygenated, and further assuming the conditions oftemperature, humidity and carbon dioxide to be stabilized, a controlledamount of oxygen containing gas is leaked into the chamber 12 throughthe inlet 64, which is actually a controlled flow rate, porous plug. Thechart recorder is moved in such a way that each increment of additionaloxygen occupies a proportional space on the chart recorder, as detectedby the oxygen electrode 60. The degree of light absorption within thespecimen in sample holder 36 is dependent upon the degree of oxygenassociation thereof. With plural, continuous readings being taken,comparator receives the signals from the photo diode 46, 50 associatedwith the respective frequencies, emitting a signal which is received bythe recorder 54 and causing the recording pin to deflect. As timeelapses, such as a twenty minute period, a trace is made of the oxygenassociation versus oxygen concentration.

According to the invention, during the time the first specimen is beinganalyzed by the light beam and the readings are taken, the secondspecimen disposed within the pocket 122 is being exposed to thecontrolled conditions of humidity, temperature and carbon dioxidereferred to earlier. This pre-conditions the specimens for more accuratereading, and although the reasons therefore are not known withcertainty, it is known that a great improvement in accuracy andreproducibility of readings is made possible.

Assuming now that the first specimen has been analyzed, the upper slide42 is pulled to the outermost position and this sample holder removed.The lower slide 74 is pushed into the innermost position, the upperslide 42 is reloaded with another charged sample holder, and the upperslide indexed to the intermediate position. Thereupon, the chamber 12 ispurged, first with oxygen and then with nitrogen, with the instrumentbeing calibrated following each purge. Thereupon the oxygen feed isagain initiated, following complete deoxygenation of the sample, and thechart recorder is activated, with the movement thereof along the axisbeing determined by the output of the oxygen electrode 60. As thisprocess takes place, another strip chart record is made, and the thirdsample is being incubated. This process may be done as many times as isnecessary.

According to the invention, incubated specimens provide the readings ofimproved accuracy referred to above, without in any way requiringadditional time from the chart recorder.

An important feature of the invention is that the samples are notadversely affected by the changing in concentrations of oxygen as thechamber 12 is purged with oxygen and nitrogen respectively at thebeginning and end of each recording. In other words, the advantages ofincubation are obtained as long as the temperature, humidity, and carbondioxide concentration are maintained approximately the same. Changingthe oxygen concentration as is necessary to obtain the readings on thesample being examined does not affect the sample being incubated. Whensample which has been incubated is to be analyzed, the chamber is purgedas set forth above. Accordingly, the invention does not require the useof additional time and does not require that special conditions beprovided within a chamber to take advantage of incubation. The novelanalysis device and slide mechanism provides for a unique and efficientmethod and very convenient means for handling the specimens. Arelatively tight seal is achieved between the moveable parts of thisapparatus and the exterior of the chamber, as set forth above. Theslides are manipulated easily and accurately by reason of the alignmentgrooves and the indexing detents with which the device is provided.

Referring now to another feature of the invention, it has beendiscovered that the use of two characteristic wave lengths in the lightsource brings about additional accuracy in analysis. According to thepresent invention, wave lengths of 576 and 560 nanometers (NM) arepreferred. These wave lengths (5760A and 5600A) particularly when usedwith one or more blue filters, as known to those skilled in the art,produce a more accurate set of readings than has been heretofore foundpossible with counterpart equivalent. It will thus be seen that thepresent invention provides a new and useful method and apparatus foranalyzing blood samples, such method and apparatus having a number ofadvantages and characteristics including those referred to specificallyherein and others which are inherent in the invention.

A preferred embodiment of the invention having been disclosed by way ofexample, it is anticipated that certain changes to the apparatus andmethods disclosed herein will occur to those skilled in the art, and itis further anticipated that such changes and modifications may be madewithout departing from the spirit of the invention or the scope of theappended claims, wherein,

What is claimed is:
 1. Method of measuring the oxygen association stateof blood samples, which includes the steps of disposing a blood samplewithin a blood-receiving receptable, providing a controlled atmospherechamber, incubating said sample by placing it in the chamber andcontrolling said atmosphere therein so as to maintain the humidity,temperature, and carbon dioxide content of the atmosphere atsubstantially constant levels, and thereafter analyzing the sample bychanging the concentration of oxygen in said chamber from time to timewhile observing the changes of oxygen association of the sample withrespect to the concentration of oxygen within the chamber.
 2. The methodas defined in claim 1 in which two samples are placed within saidchamber, with one of said samples being incubated as the other of saidsamples is being analyzed, with the incubation period comprising atleast a portion of the time period during which said other sample isbeing analyzed.
 3. The method as defined in claim 1 in which a series ofsamples is first incubated and then analyzed, with each of said samplesin said series being incubated immediately before being analyzed.
 4. Amethod as defined in claim 1 in which said analysis comprises measuringlight absorption within said sample by analysis of a light beam directedthrough at least a portion of said sample.
 5. A method as defined inclaim 4 in which said light beam includes elements having respectivewave lengths of approximately 576 nm and 560 nm (5760A and 5600A)respectively.
 6. An apparatus for incubating and analyzing bloodsamples, said apparatus comprising, in combination, means defining asample treating chamber, means for controlling the atmosphere withinsaid chamber, means for receiving at least two blood samples, saidreceiving means including first and second receiver units mounted formovement between a loading and unloading position, an incubatingposition, and an analysis position, means for directing a light beamthrough said chamber, means for detecting the degree of light absorptionof a part of said light beam by a sample placed in the path of saidbeam, and means for preventing substantial leakage of the outsideatmosphere into said atmosphere within said chamber.
 7. An apparatus asdefined in claim 6 in which said receiving units are in the form ofslides having sample holder receiving pockets therein, one of saidslides overlying the other, with both being arranged for axial movementof said respective pocket portions thereof into and out of said chamber.